Studies of the pharmacology of nociceptin/orphanin FQ (N/OFQ) and its receptor (NOP) have been hampered by the lack of a range of high potency antagonists. In this study we have examined the effects of a novel N/OFQ analogue [Nphe1,Arg14,Lys15]N/OFQ NH2 hereafter referred to as UFP-101. [3H]N/OFQ competition binding and GTPγ35S binding assays were performed using CHO cells expressing the human NOP receptor (CHOhNOP). UFP-101 (pKi of 10.14±0.09) and a range of NOP selective agonists displaced [3H]N/OFQ binding with the following rank order of affinity: [Arg14,Lys15]N/OFQ>[(pF) Phe4]N/OFQ(1–13)NH2>N/OFQ(1–13)NH2>UFP-101>N/ OFQ>Ro64–6198>[Nphe1]N/OFQ(1–13)NH2. N/OFQ, N/ OFQ(1–13)NH2, [(pF)Phe4]N/OFQ(1-13)NH2, [Arg14,Lys15] N/OFQ and Ro64–6198 also produced a concentration dependent (pEC50 values of 8.75±0.11, 9.28±0.15, 9.69±0.04, 9.12±0.11 and 8.09±0.07 respectively) and saturable stimulation of GTPγ35S binding and all were full agonists. UFP-101 did not stimulate GTPγ35S binding per se, but produced a concentration dependent and parallel rightward shift in the concentration response curves to all agonists. UFP-101 yielded pA2 values in the range 8.4–9.0. For comparison a pA2 for [Nphe1]N/OFQ(1–13)NH2 (the template for UFP-101) against N/OFQ of 7.33±0.08 was obtained. Slope factors for the Schild regression lines were ~1 indicating competitivity. When UFP-101 is compared with its template molecule [Nphe1]N/OFQ(1–13)NH2, Arg14,Lys15 substitution produced ~1 log greater potency. We suggest that due to its high potency UFP-101 should prove a further useful tool in the evaluation of the N/OFQNOP receptor system.
UFP-101, a high affinity antagonist for the nociceptin/orphanin FQ receptor: radioligand and GTP gamma S-35 binding studies
CALO', Girolamo;GUERRINI, Remo;
2003
Abstract
Studies of the pharmacology of nociceptin/orphanin FQ (N/OFQ) and its receptor (NOP) have been hampered by the lack of a range of high potency antagonists. In this study we have examined the effects of a novel N/OFQ analogue [Nphe1,Arg14,Lys15]N/OFQ NH2 hereafter referred to as UFP-101. [3H]N/OFQ competition binding and GTPγ35S binding assays were performed using CHO cells expressing the human NOP receptor (CHOhNOP). UFP-101 (pKi of 10.14±0.09) and a range of NOP selective agonists displaced [3H]N/OFQ binding with the following rank order of affinity: [Arg14,Lys15]N/OFQ>[(pF) Phe4]N/OFQ(1–13)NH2>N/OFQ(1–13)NH2>UFP-101>N/ OFQ>Ro64–6198>[Nphe1]N/OFQ(1–13)NH2. N/OFQ, N/ OFQ(1–13)NH2, [(pF)Phe4]N/OFQ(1-13)NH2, [Arg14,Lys15] N/OFQ and Ro64–6198 also produced a concentration dependent (pEC50 values of 8.75±0.11, 9.28±0.15, 9.69±0.04, 9.12±0.11 and 8.09±0.07 respectively) and saturable stimulation of GTPγ35S binding and all were full agonists. UFP-101 did not stimulate GTPγ35S binding per se, but produced a concentration dependent and parallel rightward shift in the concentration response curves to all agonists. UFP-101 yielded pA2 values in the range 8.4–9.0. For comparison a pA2 for [Nphe1]N/OFQ(1–13)NH2 (the template for UFP-101) against N/OFQ of 7.33±0.08 was obtained. Slope factors for the Schild regression lines were ~1 indicating competitivity. When UFP-101 is compared with its template molecule [Nphe1]N/OFQ(1–13)NH2, Arg14,Lys15 substitution produced ~1 log greater potency. We suggest that due to its high potency UFP-101 should prove a further useful tool in the evaluation of the N/OFQNOP receptor system.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
